You are here:
Experimental paradigm for in-lab proxy aquatic studies under conditions of static, non flow through chemical exposures
Citation:
Reddy, T., R. Flick, Jim Lazorchak, M. Smith, B. Wiechman, AND D. Lattier. Experimental paradigm for in-lab proxy aquatic studies under conditions of static, non flow through chemical exposures. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 34(12):2796-2802, (2015).
Impact/Purpose:
This paper proposes an experimental design and approach for investigators who conduct static, in-lab proxy environmental aquatic exposures to test molecular markers that will allow for the derivation of Minimal Induction Levels, i.e., method detection levels.
Description:
Endocrine disrupting chemicals (EDCs) such as 17α ethynylestradiol (EE2), 17β estradiol (E2), estrone (E1) and para-nonylphenol (NP) have been measured in wastewater treatment plant effluents, surface waters, sediments and sludge, and have been shown to induce liver-specific vitellogenin (vtg) mRNA in male fathead minnows (Pimephales promelas, FHM). The USEPA has developed a standard presence-absence bioassay for assessing estrogenicity in wastewater and surface waters using vitellogenin (vtg) gene induction in hepatic RNA extracts from fathead minnows. The purpose of our study was to establish minimal concentrations of select chemicals with known estrogen-like activity, necessary to induce transcription of vtg in 48-hour static laboratory exposures. Vitellogenin transcripts are isolated and quantified by means of quantitative real-time thermal cycle amplification (RT qPCR). Biomass loading rates of 0.5 g L-1, no aeration, and manual exchange of exposure media at 4, 8, 24, 28 and 32 hours. Adult males were exposed to EE2, E2, E1, and NP. Dose dependent increases in vtg expression were significant with all chemicals tested. Based on our results, the lowest effect concentrations of these chemicals to induce measurable vtg expression, with significant difference from respective controls were EE2, 2.2 ng L-1; NP, 13.9 g L-1 ; E2, 42.7 ng L-1; and E1, 46.7 ng L-1 measured as 48 hr average concentrations. Our observations coincide with values published in the literature, which suggests that EE2 is the most potent inducer of vtg, followed by E2, E1, and NP in descending rank order. It should be noted that onset of effects from low concentration exposures can vary significantly with respect to route of bioavailability, as well as the duration of exposure. The suggested values are only for 48-hour exposures, which is the historical duration for aquatic lab exposures conducted by the Agency. We use the current experimental design to propose guiding principles for investigators who conduct static, in-lab proxy environmental aquatic exposures. Specifically, we appeal for the conception of Minimal Induction Levels under the described method of exposure.